Reading the survey, I see there is really only one choice... but I kind of have a different approach to some... maybe most even...
I HAVE 5 echo products. 1 Original Echo, and 4 Dots. I do have several Fire Tablets as well as an amazon Fire Stick too... but they're not truly official Echo Products.
If I were limited to Just one (and having my knowledge and experience with Nearly all of them now) I would Still Buy the original Echo or 2nd Gen echo. Basically the same unit in different packages... Yeah, the new one has better sound... so Likely would win out as First "only choice".
I set my Echosystem up this way - My "MAIN" unit is with me and my computer - All the rest are used as satellites but are capable of everything on their own. The sound is better on the Full Echo, so it is the only one I use for music. The rest are mostly for Smart home controllers as I have 17 Hue Bulbs and devices with plans for more. It is truly a convenience for my In-Laws as they're able to turn lights on/off without getting up to activate a switch. My wife loves the voice control and motion sensors to help her while she has her hands full working around the house. If it weren't for the old people I'd buy one of the Smart Automated vacuum systems as well, to reduce the work load my wife takes on. I also use the "Master" one to control TV nearby, so I can see what's going on, since none of my AV system has a way to check Status from the Echo's.
Other than that I don't think any one fits my needs any better than the rest, and my wife expresses no interest in having a SHOW, or any other devices... yet. Once she figures out the voice control for the Show and recipes... It could be a deal changer for sure.
The funniest thing about this Survey is no one here would buy the dot as their only Echo... but several of us have even stated that we own more of them than any other Echo Product...